RESUMO
Histological examination was carried out on 100 cases of small round- cell tumors in children. The capacity of immunohistochemical staining to increase diagnostic accuracy was assessed, using antibodies against leucocyte-common antigen [LCA], neuron-specific enolase [NSE] and myoglobin. The immunohistochemistry helped in correcting the diagnosis in 7% of cases. The final diagnosis of the 100 cases was non-Hodgkin's lymphoma [NHL, 50%], neuroblastoma [NBLO, 29%], Ewing's sarcoma [13%] and embryonal rhabdomyosarcoma [ERMS, 8%]. All cases of NHL were positive for LCA regardless of the histologic type. NSE was demonstrated in all cases of NBL regardless of the histologic grade. Myoglobin was detected in 62.5% of cases of ERMS. Staining for myoglobin correlated with rhabdomyoblastic differentiation regardless of histologic type. All cases of Ewing's sarcoma did not react with the three antibodies used. This study indicated that although immunohistochemistry provides a useful tool in the diagnosis of small round-cell tumors, yet it has to be combined with electron microscopy to increase the frequency of diagnosis especially in cases of ERMS and Ewing's sarcoma